(CNN) -- Americans are already among the fattest people in the world, and they just keep packing on the pounds. A new report finds that obesity rates have swelled during the last year in 31 states with not one state reporting that its obesity rate shrank.

Two-thirds of U.S. adults are obese or overweight, according to the Trust for America's Health.

And, for the first time, more than 30 percent of residents in one state -- Mississippi -- are classified as obese.

Nationwide, two-thirds of U.S. adults are obese or overweight, according to the fourth annual report from the Trust for America's Health, titled "F as in Fat: How Obesity Policies are Failing in America." The report's co-author says the government needs to treat this trend as an epidemic that threatens the health of Americans and put in place a national plan to combat obesity.

"The key recommendation in the report is we need a national strategy," said report co-author Jeffrey Levi.

"We need something like that in obesity that says this is what every agency of the federal government is doing. [It's] what we can do to directly affect this problem and motivate individual communities and businesses to play their role as well," Levi said.

In 32 states, 60 percent of the population is either overweight or obese. West Virginia ranks highest in the combined statistic, with nearly two-thirds of its adults obese or overweight.

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The Trust for America's Health suggests these programs might help cut obesity in the U.S.: Expand the Agriculture Department's Fresh Fruit and Vegetable Snack program, which last year was used in just 400 schools in 14 states. Restrict the sale of junk food in schools. Increase food stamp benefits so recipients can afford fruits and vegetables Subsidize farmers' markets to take Electronic Benefits Transfer cards from the Food Stamp Program Give financial incentives to create more farmers' markets Source: Trust for America's Health

Mississippi, where almost one in three adults are obese, also ranks highest in adult hypertension and physical inactivity. It's tied with the District of Columbia in poverty and ranks second-highest in adult diabetes.

West Virginia came in second in the obesity ranking, followed by Alabama, Louisiana, South Carolina and Tennessee.

Nationwide, more than 25 percent of adults in 19 states are obese, up from 14 states last year.

"If you go back to 1991, only four states had obesity rates above 15 percent, and none exceeded 20 percent," said Levi.

Physical activity is linked to a reduced risk of dying prematurely. It also lowers one's risk of developing a host of diseases, including heart disease, diabetes, high blood pressure and colon cancer.

Obesity also affects the health of the nation's economy. Fat employees translate into fat medical bills for U.S. businesses trying to compete in an international marketplace.

A Duke University study that appeared in the Archives of Internal Medicine found 184 lost workdays per 100 obese full-time employees versus 14 lost workdays per 100 normal-weight full-time employees.

The average obese worker has up to 21 percent higher health care costs, the Duke report said.

A Medicare study found that obese patients cost the agency 15 percent more than normal or overweight patients.

Levi says individuals need the government's help to take control of their weight.

"People can't exercise personal responsibility in a vacuum," he said. "If you're telling people to eat healthier food and there are no grocery stores in the neighborhood; if you're telling them to be more physically active, and they live in poor, unsafe neighborhoods or in suburban neighborhoods with no sidewalks, then you've created an environment that doesn't make it possible for people to exercise that personal responsibility. That's where government plays a role."

And it's not just government agencies involved in public health that need to play a role, he said. Zoning boards are involved in building the sidewalks that encourage people to walk; school boards are involved in ensuring students get nutritious meals and physical education programs, he said.

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"Everyone has a role to play, starting with though not ending with the federal government," he said, noting that funding for relevant federal programs has been flat in recent years.

"The resources are definitely not commensurate with the problem," he said. "Lots of people share the blame here."

The CDC's point man on obesity, Dr. William Dietz, said he could see no drawbacks to the appointment of an obesity czar who would coordinate federal programs.

But, he added, "That's a difficult issue for me to comment on because it's a recommendation for the administration that I'm part of."

Still, no single strategy will solve the problem, he said, noting that dozens of societal changes are linked to the nation's expanding waistline -- the greater availability of food, an increase in television viewing, cheaper prices for food, and more availability of soft drinks.

But diabetes specialist Dr. Richard K. Bernstein worried that an obesity czar might lead the nation down the wrong path.

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The New York-based author of "Diabetes Solution," contends that the popularity of low-fat diets is related to the increase in diabetes and obesity.

"Insulin stores fat," he said. "Eat very little carbohydrate, you're gong to make very little insulin. Not only will you not store fat, you'll metabolize it."

A senior analyst for The Center for Consumer Freedom, a food industry trade group, said government involvement is not needed. "Obesity is a private issue and we do not need Big Brother wagging his finger at us every time somebody wants to eat a doughnut," said Justin Wilson. "If someone wants to be a little heavier because they enjoy eating food that tastes good, that's a person's personal right."

He cited two simple ways for people to lose weight -- "closing their mouth, going for a walk. It's the world's easiest diet plan."

The study was carried out by the Trust for America's Health, which Levi directs. It describes itself as a nonprofit, nonpartisan organization "dedicated to saving lives by protecting the health of every community and working to make disease prevention a national priority."